JSGF compiler produces copious epsilons

[David Huggins-Daines]

This isn't, in itself, a problem, as it is necessary in order to produce correct grammars, but it becomes one because the epsilon closure that's done in fsg_model.c is quite inefficient.

Either we need to do epsilon removal on the output of the JSGF compiler, or simply do it instead of epsilon closure for all FSGs. The algorithm is pretty simple and extremely well documented...